[chore](Nereids) create policy always allow fallback (#33226)

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/commands/CreatePolicyCommand.java

@@ -79,6 +79,7 @@ public class CreatePolicyCommand extends Command implements ForwardWithSync {
 
     @Override
     public void run(ConnectContext ctx, StmtExecutor executor) throws Exception {
+        ctx.getSessionVariable().enableFallbackToOriginalPlannerOnce();
         throw new AnalysisException("Not support create policy command in Nereids now");
     }
 }